In the manufacture of semiconductor devices and other products, ion implantation systems are used to impart impurities, known as dopant elements, into workpieces, such as semiconductor wafers, display panels, or other workpieces. Conventional ion implantation systems or ion implanters treat a workpiece with an ion beam in order to produce n- or p-type doped regions, or to form passivation layers in the workpiece. When used for doping semiconductors, the ion implantation system injects a selected ion species to produce the desired extrinsic material. For example, implanting ions generated from source materials such as antimony, arsenic, or phosphorus results in n-type extrinsic material workpieces. Alternatively, implanting ions generated from materials such as boron, gallium, or indium creates p-type extrinsic material portions in a semiconductor workpiece.
Conventional ion implantation systems include an ion source that ionizes a desired dopant element which is then accelerated to form an ion beam of prescribed energy. The ion beam is directed at a surface of the workpiece to implant the workpiece with the dopant element. The energetic ions of the ion beam penetrate the surface of the workpiece so that they are embedded into the crystalline lattice of the workpiece material to form a region of desired conductivity. The implantation process is typically performed in a high vacuum process chamber which helps to prevent dispersion of the ion beam by collisions with residual gas molecules and which minimizes the risk of contamination of the workpiece by airborne particulates.
The workpiece is typically introduced from atmosphere into the process chamber via a load lock chamber, wherein the workpiece is placed on an electrostatic chuck (ESC) within the process chamber, and generally held in place by electrostatic forces induced between the electrostatic chuck and the workpiece. When ion implantation is complete, the workpiece is removed from the ESC and placed back in the load lock chamber, or placed in another load lock chamber. In typical ion implantation processing, the ion beam is shut off after the implantation in order to prevent contamination within the process chamber, as well as energy savings, etc.
It is common, however, to intermittently adjust the ion beam, wherein a faraday cup along the beamline of the ion beam is utilized to measure properties of the ion beam, such as current, in order to “tune” the ion beam to acceptable parameters. During tuning, the ion beam strikes the faraday cup, and potentially sputters material from the faraday cup into the process chamber. Furthermore, during tuning, a clamping surface of the electrostatic chuck is typically exposed to such sputtered material, wherein the sputtered material can contact and/or build up on the clamping surface of the electrostatic chuck. However, it is generally undesirable to have a workpiece residing on the clamping surface of the electrostatic chuck during said tuning, since the sputtered contaminants have a high probability of causing defects on the workpiece, thus leading to losses in production.
Therefore, a need exists for a device for protecting the clamping surface of the electrostatic chuck during tuning, wherein sputtered material is generally prevented from contacting the clamping surface of the ESC.